Error: Continuous value supplied to discrete scale

Question

I'm trying to make a heat plot for a discrete outcomes (each value uses a single color) such that:

df<-data.frame(x=rep(LETTERS[1:10], each=10), 
               y=rep(1:10,10),
               value=sample(1:8, 100,replace=T))
colors<-c("green", "lightyellow", "yellow", "orange", "orangered", "red", "darkred", "black")
ggplot(df, aes(x=x, y=y))+
    geom_tile(aes(fill=value), colour="white")+
    #scale_fill_gradient(low="green", high="red")
    scale_fill_manual(values=colors)
Error: Continuous value supplied to discrete scale

Does somebody know how to fix it and apply the colors variable to the heatmap?

Solution

If you want to supply colours manually, you need to map fill to a factor variable.

ggplot(df, aes(x=x, y=y))+
  geom_tile(aes(fill=factor(value)), colour="white")+
  scale_fill_manual(name = "Values", values=setNames(colors, 1:8))